Designers of vertical and short take-off and landing aircraft (V/STOL aircraft) have proposed a variety of structures for controlling the direction of engine exhaust flow during the translation from vertical to conventional horizontal flight. Certain of these systems have in fact become operational, but in general they have suffered inefficiencies in terms of fuel consumption and effective thrust. Additionally, the mechanisms employed, such as variable geometry exhaust ducts and actuating mechanisms, have been undesirably complex. As will be understood by those in the art, substantial thrust forces are required in V/STOL propulsion systems since, during take-off and substantially vertical flight modes, the total downwardly directioned thrust forces must equal, and at times exceed, the total weight of the aircraft. Accordingly, the exhaust ducts sustain substantial loads when directioning or "vectoring" the exhaust gases. Because of this requirement for substantial structural strength and because of the complexity of construction of articulated exhaust duct structures and the corresponding actuating and control systems, many of the prior-art propulsion systems have themselves introduced an undesirable degree of additional weight, along with substantial complexity and costs.
One such prior-art system, disclosed in U.S. Pat. No. 2,951,660, employs a variable geometry exhaust deflector structure which extends rearwardly from the aft exhaust duct of a jet engine housing. A series of articulated segments are provided, supported by a series of linkages connected to the aircraft structure and to each of the segments. The series of segments is translated from a horizontal orientation (in which the segments are aligned horizontally and extend rearwardly from the engine exhaust nozzle) and a downwardly deflected and curved orientation. When the deflector structure extends downwardly, the engine exhaust impinges against the segments and is deflected downwardly for providing increased lift. It will be understood by those in the art that the loads sustained by such linkage elements and articulated segments are cumulative, or additive; that is, those linkage elements and ramp segments nearest the aircraft structure must sustain not only the forces exerted by the engine exhaust impinging against them, but also those forces exerted against the remaining, aft segments. Thus, the linkages, duct segments, and actuators must be of substantial structural stength to sustain the operational loads. It will also be understood that, during operation over extended periods of time, substantial vibrational and environmental loads will be sustained by the various movable elements.
VSTOL power plants have also employed various other complex actuating and supporting structures for directioning exhaust flow. The system disclosed in U.S. Pat. No. 3,700,189, for example, includes at least two propulsive fan units each including a respective engine, the fan units being pivoted, within engine pods, between horizontal and vertical orientations for providing horizontal and vertical thrust. Other aircraft have employed multiple exhaust nozzles which project from side portions of the aircraft fuselage and which are pivoted between horizontal and substantially vertical orientations.
It is highly desirable in such VSTOL Propulsion Systems that the downwardly directioned exhaust flow be distributed so that the net upward reactive force is substantially in coincidence with the center of mass of the aircraft. To accomplish this, many of the prior-art systems employ two, three, or four exhaust nozzles positioned laterally around the center of mass and arranged for providing net downward thrust at the center of mass. As an example, one military attack aircraft employs pairs of exhaust nozzles which project to the left and the right of the fuselage, the nozzles having swivel joints which permit pivotal rotation of the respective exhaust nozzles about generally horizontal axes, whereby the nozzles are pivoted from a horizontal orientation to a downwardly projecting orientation. The use of such multiple, laterally arranged exhaust nozzles, to provide net lift forces coincide with the center of mass, results in increased drag and weight, and multiple actuation and control mechanisms are necessary for positioning the several nozzle structures. In summary, prior-art systems have in general suffered from a number of structural and operational limitations.
It is, accordingly, a major object of the present invention to provide a new and improved propulsion system adapted for use in V/STOL Aircraft.
Another major object is to provide a propulsion system which is adapted for deflecting or vectoring thrust of aircraft in flight (including conventional aircraft not having vertical flight characteristics) for enhancing the performance and maneuvering capabilities of the aircraft.
Another object is to provide such a propulsion system having apparatus for directioning exhaust gases generated by a jet propulsion engine, which system is of simplified, rugged construction, having relatively few moving elements.
A further object is to provide such a propulsion system having a variable geometry exhaust deflection structure which does not entail the use of a multi-element linkage structure for supporting and positioning the structure.
Yet another object is to provide such a system which is adapted for integral construction in a jet engine housing and in which the variable geometry exhaust deflection system is of aerodynamically efficient configuration.
Still another object is to provide such a system which requires only one exhaust duct structure.
Another object is to provide such a structure which is of practicable construction, adapted for reliable operation under severe environmental and operational conditions.
Other objects and advantages will be apparent from the specification and claims and from the accompanying drawing of a preferred embodiment of the invention. While a preferred embodiment, along with modifications thereof, is described and illustrated in detail herein by way of example, it should be understood that various other embodiments and applications of the system may be made without departing from the scope of the invention, as defined in the accompanying claims.